1. Field of the Invention
The present invention relates to a method of locking the functions of a mobile telephone system, and more particularly, to a method of locking the functions of a mobile telephone system in which at least two lock codes are stored and when releasing the locked state, keeping some functions in the locked state in accordance with the lock code and actuating the other functions.
2. Description of the Prior Art
Mobile telephone systems have increasingly come into general use with the current extensive use of the automobile and the need to conduct business expeditiously, as well as from the viewpoint of security, and so forth. A mobile telephone system which is called the cellular system has been developed and come into wide use, especially in the U.S.A. The cellular system is a method of communicating with receivers at various stations by dividing a service area into a plurality of cells of about 6.4 Km in radius, in each of which a wireless telephone station (base station) is provided. Telephone calls are operated by wireless contact between successive base stations in a service area and the telephone provided within a car as the car travels to different areas. This system enables communication over a wide area, as well as allowing the number of channels to be increased, and the number of circuits to be increased without limit.
In such a cellular mobile telephone system, it is possible to communicate with a caller and also to make an external call from the mobile telephone system to an outside station while the ignition switch and the power switch are kept on.
Furthermore, the cellular system telephone system enables all the functions of the mobile telephone system to be kept in the locked state (non-actuated state) in which it is impossible to answer any call or to call any person until a predetermined lock code is input.
However, in a conventional mobile telephone system, which has only one kind of lock code, it is impossible for someone to use all the functions of the mobile telephone system and for others to use a limited number of functions.
For example, it is convenient if it is possible that (a) the owner of the car can use all the functions of the mobile telephone system without limitation, e.g., to call any number, even a long-distance one and to answer any call, while (b) the owner's family and friends have the ability solely to call local telephone numbers, not long-distance ones, and have no ability to answer any long-distance call (since the fee is paid by the receiver in U.S.A). It is impossible, however, for a conventional telephone system to answer such a demand.